You're overstating the have to be ABs to earn a living a bit. If that was actually the case we wouldn't be able to form any teams in Super Rugby or the NPC. Yet there are 5 Super Squads, WTG, and back up players, and then 14 NPC teams. Even a small province like mine, Hawkes Bay, has a majority of Super players so they're getting their main money there and the NPC is an add on.
As I've said previously in this thread the boom time for snatching up rugby players was when the Holden Cup was running as young guys under 20 could get a little bit of money as opposed to no money.
To give a little bit of perspective, Tohu Harris signed with the Storm after he was not offered an Academy spot with Hawkes Bay. Obviously it was clearly the right decision, I think his style is more suited to league, but I think it's reminder to not take it for granted that young rugby players all will switch to league.